Field of the Invention
The present disclosure relates to channel estimation in wireless networks. More specifically, the present disclosure relates to a system and method for disintegrated channel estimation in wireless networks.
Related Art
In the field of wireless telecommunications, providing communications channels that are reliable and of high quality of service are paramount concerns. Cooperative communication has become one of the most essential aspects of recent mobile communication. A relay network represents one form of cooperative communication and has attracted a large amount of research in recent years. A space-time coding technique supported by relays has, in the past, been employed to achieve spatial diversity. The achievable diversity obtained using cooperative networks was studied previously. It has been found that the relay nodes alter the received signals according to the space-time block code (STBC) arrangement and then send the resultant signals to the destination node. The diversity achieved using the distributed STBC (D-STBC) with relays can be achieved by accurately estimating multiple timing errors and multiple frequency offsets as well as acquiring precise knowledge of the channel state information (CSI). Additionally, previous studies have successfully addressed the problems caused by timing errors and frequency offsets.
To acquire accurate knowledge of CSI, several channel estimation techniques have been investigated previously. These techniques are often categorized as (1) cascaded channel estimation; and (2) disintegrated channel estimation. However, cascaded channel estimation is ineffective for several applications such as optimal relay matrix design and beamforming. In existing relay beamforming techniques, relay gains were adjusted to suppress interference. Concerning disintegrated channel estimation, two methods are usually adopted to obtain disintegrated CSI at the destination node. In the first method, the source-relay channels are estimated at the relay nodes first by means of a conventional single-hop channel estimation, and the estimates are then quantized, compressed and sent toward the destination node via dedicated channels. Thus, the relay nodes are required to conduct source-relay channel estimation and compression with high complexity, and additional time slots or subchannels are required to deliver the source-relay estimates, decreasing both the spectral and energy efficiencies. In the second method, both the source-relay and the relay-destination channels are estimated at the destination node. A method utilizing relay pilots to conduct disintegrated channel estimation was studied previously, in which several pilot subcarriers are preserved for sending the relay pilots. It was found that the destination node can estimate the source-relay-destination and the relay-destination channels by exploiting the source and the relay pilots, respectively. The orthogonality requirement of the relay pilots was addressed in a previous study. In addition, the orthogonality was exploited to generate training sequences that can be applied in an amplify-and-forward (AF) relay network. Because prior efforts only studied a disintegrated channel estimation in a single-relay network, generalizations and improvements of the disintegrated channel estimation techniques in multiple cooperative relay network are strongly desired.
Accordingly, what would be desirable is a system and method for disintegrated channel estimation in wireless networks, which addresses the foregoing shortcoming of existing systems.